Magnetic Bearing, a new type of bearing, have been regarded widely in the field of engineering and science because of its excellent performances, non-contact,high speed,long life, lubricant, and broad application , as one of reseach objects in the field of mechan-electronical engineering and control. The history, category ,advantages, research status ,control methods and development trend are presented,as well as some problems which need more studies. The research is emphasized in the application and digital control technologies of DC active magnetic bearing in high power and high speed rotary machines.